1. Field of the Invention
The present invention relates to a method for managing download of contents in communication terminals such as portable telephones, and more particularly, to a method for managing download of the same contents as already-stored contents in communication terminals.
2. Description of the Related Art
With the recent developments in the communications industry, services provided by mobile communication systems have evolved into a multicasting multimedia service which transfers large-sized data such as packet data, circuit data, and the like, as well as provides a voice service.
Recent communication terminals have functions and programs comparable to personal computers. Portability and improved functions of the communication terminals themselves promote the use of additional functions by users. Basically, the communication terminals are able to store a considerable amount of data, such as telephone numbers and personal schedules, and output and edit the data as necessary.
In recent years, the communication terminals have become able to store and provide large-sized multimedia data, such as music, games and movies. For example, the communication terminals have functions of downloading and replaying various bell sounds or music files, which are not stored by the manufacturers, via an external communication interface from external communication devices, such as computers, or sound providers. The present invention is directed to a method for managing download of and replaying various content data using a communication terminal.
A communication terminal generally includes a data storage memory for storing contents provided by content providers and a usage-right storage memory for storing information about a right to use downloaded contents. The usage-right storage memory is called a replay cache memory and is hereinafter referred to simply as a replay memory.
The following is an example of a conventional replay memory that stores information about a right to use downloaded contents.
Open mobile alliance (OMA) digital right management (DRM) v2.0 specification specifies that a communication terminal has a replay cache memory to prevent downloaded contents from being replayed a limitless number of times. Thus, the communication terminal manages a globally unique right object (RO) identifier (GUID) and a right issuer timestamp (RITS) of contents.
For this, prior to downloading the contents, the communication terminal constructs the globally unique right object identifier (GUID) and the right issuer timestamp (RITS), provided by the content provider, as a table having a tree format, and stores and manages the table.
For reference, right related information including the globally unique right object identifier (GUID) includes content right information and content encryption key (CEK) information for decrypting encrypted contents. The information is used to decode the downloaded contents at the communication terminal. The information is forwarded to the communication terminal prior to downloading the content.
Examples of the right information include permission and constraints for contents. The permission information includes play, display, execute, print, and export. Further, the constraints include count, time-count, date time, interval, accumulated, individual, and system.
Among the above information, a content play right will be described herein. However, the present invention is likewise applicable to the other information.
The following is an example of a conventional method for managing download of contents in a communication terminal using the replay memory.
First, a communication terminal receives a right object (RO) containing a right issuer timestamp (RITS). The communication terminal then compares a content provision time included in the right issuer timestamp (RIFS) to a current time set in the communication terminal plus 24 hours. Here, the current time set in the communication terminal plus 24 hours is a reference time set to determine whether the right object (RO) is wrong.
If the content provision time is determined to be more than the current time set in the communication terminal plus 24 hours, the communication terminal determines based on time information provided by a base station whether the current time set in the communication terminal is correct. If the set current time is determined to be incorrect, the communication terminal accurately synchronizes the current time with the time provided by the base station.
If it is determined in that the set current time is correct, the communication terminal ignores the received right object (RO) and does not download content corresponding to the right object (RO) destined to be provided by the content provider.
On the other hand, if it is determined that the content provision time is not more than the current time set in the communication terminal plus 24 hours, the communication terminal compares the received right object (RO) to an entry stored in the replay memory. Specifically, the communication terminal determines whether the globally unique right object identifier (GUID) and the right issuer timestamp (RITS) corresponding to the received right object (RO) exist as entries in the replay memory.
If the globally unique right object identifier (GUID) and the right issuer timestamp (RITS) corresponding to the received right object (RO) are determined to exist as the entries in the replay memory, the communication terminal ignores the received right object (RO) and does not download the content corresponding to the right object (RO) destined to be provided by the content provider.
If it is determined in that the globally unique right object identifier (GUID) and the right issuer timestamp (RITS) corresponding to the received right object (RO) do not exist as the entries in the replay memory, the communication terminal recognizes that there is no same content information in the replay memory and determines whether there is an empty space in the replay memory. If it is determined that there is an empty space in the replay memory, the communication terminal accepts the received right object (RO) and stores the globally unique right object identifier (GUID) and the right issuer timestamp (RITS) corresponding to the received right object (RO) in the replay memory.
On the other hand, if it is determined that there is no empty space in the replay memory, the communication terminal determines whether the right issuer timestamp (RITS) of the received right object (RO) is earlier than the oldest entry stored in the replay memory. If the right issuer timestamp (RITS) of the received right object (RO) is earlier than the oldest entry stored in the replay memory, the communication terminal ignores the received right object (RO) and does not download content corresponding to the right object (RO) destined to be provided by the content provider.
On the other hand, if it is determined in that the right issuer timestamp (RITS) of the received right object (RO) is not earlier than the oldest entry stored in the replay memory, the communication terminal deletes an entry having the oldest right issuer timestamp (RITS) stored in the replay memory. The communication terminal then accepts the received right object (RO) and stores the globally unique right object identifier (GUID) and the right issuer timestamp. (RITS) of the received right object (RO) in an empty space of the replay memory from which the entry having the oldest right issuer timestamp (RITS) has been deleted.
Although a right for content paid and used by a user is about to expire, i.e., when the content has been replayed nine times and only one replay remains, the user might like to replay and listen to the content more than just once more. Normally, the user is allowed to re-purchase the same content when there is no remaining available replay count. However, in some cases the user may like to purchase the content in advance even when an available replay count remains.
When the user makes a download request for the same content, the communication terminal refuses a received right object (RO) and does not download the content since the existing downloaded globally unique right object identifier (GUID) and right issuer timestamp (RITS) entries remain in the replay memory. Thus, there is a need for a scheme to newly update an existing allocated use right (e.g., replay time) so that the same content is downloaded in duplicate even though the right is not all used and there remains content right related information in the replay memory.